RNA interference (RNAi) is a mechanism by which double-stranded RNA triggers the silencing of target gene expression by inducing sequence-specific target mRNA degradation. In certain instances, short interfering RNAs (siRNAs), dsRNA duplexes of 21-23 nucleotides, are mediators in the RNAi pathway that lead to degradation of specific mRNAs through the RNA induced silencing complex (RISC). Once introduced into cells, siRNA molecules bind to Argonaute2, a component of RISC, that catalyzes the cleavage of the target mRNA.